Hey guys,
as stated abobe, after updating the plex server to the latest build my xbox one DOES apper on the webinterface as target to cast to, but fails in doing so. Also the xbox does not appear on all of my iOS devices using them to redirect from the server to the xbox as a remote.
LOVED that feature. 
Checked the logfiles and after having updated there are tons of entries likes these:
Feb 10, 2017 04:09:11.762 [8536] WARN - [Plex for Xbox One] [Companion] Poll failed to Desktop; testing all connections
Feb 10, 2017 04:09:12.060 [8536] WARN - [Plex for Xbox One] [Connections] Desktop is unavailable at http://192.168.10.89:32400/ (Status 0)
Feb 10, 2017 04:09:12.109 [8536] WARN - [Plex for Xbox One] [Connections] All connections to Desktop failed
Feb 10, 2017 04:09:12.158 [8536] WARN - [Plex for Xbox One] [Companion] Poll failed to Desktop; unable to reconnect
Feb 10, 2017 04:09:12.206 [8536] WARN - [Plex for Xbox One] [Companion] Poll failed to Desktop; attempting to pick new proxy
Feb 10, 2017 04:09:12.252 [8536] WARN - [Plex for Xbox One] [Companion] No proxy found
and
Feb 10, 2017 04:10:50.596 [6508] DEBUG - Request: [::ffff:192.168.10.101:51952 (Subnet)] GET / (12 live) GZIP Signed-in Token (myusername)
Feb 10, 2017 04:10:50.598 [6508] DEBUG - (Capabilities) Platform ‘Xbox One’ not matched by plugin platform requirements
Feb 10, 2017 04:10:50.599 [6508] DEBUG - It took 0.0 sec to serialize a list with 19 elements.
Feb 10, 2017 04:10:50.795 [2220] DEBUG - Request: [::ffff:192.168.10.101:51952 (Subnet)] GET /player/proxy/poll?deviceClass=pc&protocolVersion=1&protocolCapabilities=timeline%2Cplayback%2Cnavigation%2Cmirror%2Cplayqueues (12 live) GZIP Signed-in Token (myusername)
Feb 10, 2017 04:10:50.796 [2220] DEBUG - Beginning read from two-way stream.
and basically all sub-processes ending with:
Feb 10, 2017 04:12:33.442 [1272] ERROR - handle_stream_read error 2 End of file
after they REALLY tried hard to swap over, they state this one again:
Feb 10, 2017 04:13:32.224 [3440] DEBUG - (Capabilities) Platform ‘Xbox One’ not matched by plugin platform requirements
and the whole game restarts.
I know the process ids in these logs do not match, please understand it as a compressed view over many different parallel polls.
Playing directly from the xbox works like a charm.
Xbox App not compatible to the rest of the family?
Maybe you guys have an advice? 
Thanks!
Oh - and great job, i really appreciate your effort, love Plex for working out of the box over all my devices!
regards,
G.
